4 stroke engine

A 4-stroke engine works through four distinct stages (or "strokes") of the piston inside the cylinder. These four strokes are:

1. Intake Stroke

Purpose: Draw air-fuel mixture (in gasoline engines) or just air (in diesel engines) into the cylinder.

What happens:

The intake valve opens.

The piston moves down from top dead center (TDC) to bottom dead center (BDC).

This creates a vacuum that pulls in the air-fuel mixture.

2. Compression Stroke

Purpose: Compress the air-fuel mixture to increase its energy potential.

What happens:

The intake valve closes.

The piston moves up from BDC to TDC.

This compresses the mixture, making it more volatile.

3. Power Stroke (Combustion Stroke)

Purpose: Generate power to move the vehicle.

What happens:

At the top of the compression stroke, a spark plug ignites the compressed air-fuel mixture (in gasoline engines). In diesel engines, fuel is injected into compressed hot air, causing auto-ignition.

This explosion forces the piston down, producing mechanical energy that turns the crankshaft.

4. Exhaust Stroke

Purpose: Expel burnt gases (exhaust) from the cylinder.

What happens:

The exhaust valve opens.

The piston moves up from BDC to TDC again.

This pushes the spent gases out through the exhaust valve.